Rhubarb Oatmeal Muffin Cake is a great old-fashioned breakfast cake recipe. It’s easy to make, bursting with juicy rhubarb and has a great texture from the oats.

Muffins are a wonderful thing! They're so easy to make, taste really good and are great for breakfast or taking in a lunch box to work or school. However, sometimes you want more than a muffin, or you don't have any muffin liners. This is when this easy muffin cake comes in to save the day!
This idea came about because my neighbor had given me a handful of rhubarb from her garden and I decided to make some muffins.
Well, I got as far as making the batter, and my muffin cases were no where in sight. So I ended up using an 8 inch square pan. I have to say, eating a slice of this cake for breakfast was delicious!
This site contains affiliate links. I may receive a commission for purchases made through these links. As an Amazon Associate I earn from qualifying purchases. For more information, check Privacy Policy.

The texture of the crumb is light and fluffy, and with the addition of oats, it gives the cake a little chewy-ness, but only slightly. It also makes it a bit more filling by adding oats.
The rhubarb is a little tangy, which is perfect against the sugar in the cake. Note, I haven't used much sugar as I was making this for breakfast, but you can by all means add say another 25% sugar if you prefer a sweeter cake. The rhubarb adds a juiciness and extra moisture to the cake too. So you certainly won't have a dry cake! You can of course use this same recipe and swap the rhubarb for other berries when they're in season, for example, strawberries, blueberries or raspberries.

I haven't added a topping on the cake. I didn't find it was necessary, but perfectly tasty as it is. If you wanted to make this as a dessert cake, I would suggest serving it with some warm custard, or lemon whipped cream. Either of those flavor combinations will work well with the rhubarb.
The recipe itself is very easy, you just need to make the cake batter in the usual way you make muffins by combining the wet and dry ingredients. The baking will take a little longer as it is a square pan we're using. If you wanted to make it in a loaf pan, you'll need to bake for around 55 - 60 minutes. As always, check with a skewer to make sure it's cooked in the middle.
Check out our handy Oven Temperature Conversion Guide!
Prep Time
20 Minutes
Bake Time
45 Minutes
Serves
12
Ingredients
Dry Ingredients
1 & ½ cups or 180 g All-Purpose / Plain Flour
½ cup or 100g Regular Sugar
½ teaspoon salt
1 tablespoon baking powder
½ cup or 45g rolled oats, old-fashioned or quick-cooking
Wet Ingredients
1 cup or 220 ml milk
2 Tablespoons lemon juice
⅓ cup or 65 ml vegetable oil
2 large eggs
1 teaspoon vanilla extract
1 Stick of Rhubarb
Instructions
1. Preheat the oven to 400 F or 200 C. Grease an 8 inch square pan.
2. In a bowl, add the milk and lemon juice, stir and then add the oatmeal.
3. Stir in the oats very well so they can all soak and become soft.
Then add the remainder of the wet ingredients and using a fork, beat so the eggs are well combined with the rest of the wet ingredients. Set aside.
4. In a separate large bowl, measure out the remaining dry ingredients and combine so everything is mixed in well.
5. Add the wet ingredients to the dry ingredients, and stir just enough until combined. Make sure you do not over cmix as this will toughen the muffins.
6. Wash the rhubarb and then cut the ends off. Then cut into 1-inch pieces.
7. Transfer cake batter to the greased baking pan
8.Arrange the cut rhubarb on top of the batter. DOn’t push the rhubarb down, it will naturally sink a little.
9. Bake for 45 minutes, until golden brown and the cake tester comes out clean.
10. Remove from the oven and allow to cool in the pan for 5 minutes and then transfer to a cooling rack.
11. Serve whilst warm or store in an air tight container.
We'd love to hear from you and what you thought of our recipe. Did you make any changes or add some other ingredients? Let us know in the comments below. Thanks for reading and happy cooking!

Recipe Card

Rhubarb Oatmeal Muffin Cake
Rhubarb Oatmeal Muffin Cake is a great old fashioned breakfast cake! It’s easy to make, bursting with juicy rhubarb and has a great texture from the oats.
Ingredients
Dry Ingredients
- 1 & ½ cups or 180 g All-Purpose / Plain Flour
- ½ cup or 100g Regular Sugar
- ½ teaspoon salt
- 1 tablespoon baking powder
- ½ cup or 45g rolled oats, old-fashioned or quick-cooking
Wet Ingredients
- 1 cup or 220 ml milk
- 2 Tablespoons lemon juice
- ⅓ cup or 65 ml vegetable oil
- 2 large eggs
- 1 teaspoon vanilla extract
- 1 Stick of Rhubarb
Instructions
- Preheat the oven to 400 F or 200 C. Grease an 8 inch square pan.
- In a bowl, add the milk and lemon juice, stir and then add the oatmeal.
- Stir in the oats very well so they can all soak and become soft.
- Then add the remainder of the wet ingredients and using a fork, beat so the eggs are well combined with the rest of the wet ingredients. Set aside.
- In a separate large bowl, measure out the remaining dry ingredients and combine so everything is mixed in well.
- Add the wet ingredients to the dry ingredients, and stir just enough until combined. Make sure you do not over cmix as this will toughen the muffins.
- Wash the rhubarb and then cut the ends off. Then cut into 1-inch pieces.
- Transfer cake batter to the greased baking pan
- Arrange the cut rhubarb on top of the batter. DOn’t push the rhubarb down, it will naturally sink a little.
- Bake for 45 minutes, until golden brown and the cake tester comes out clean.
- Remove from the oven and allow to cool in the pan for 5 minutes and then transfer to a cooling rack.
- Serve whilst warm or store in an air tight container.
Recommended Products
As an Amazon Associate and member of other affiliate programs, I earn from qualifying purchases.
Nutrition Information:
Yield: 12 Serving Size: 1Amount Per Serving: Calories: 168Total Fat: 7gSaturated Fat: 1gTrans Fat: 0gUnsaturated Fat: 5gCholesterol: 33mgSodium: 232mgCarbohydrates: 24gFiber: 1gSugar: 10gProtein: 4g
Nutrition information isn’t always accurate
Sheet Pan Style Cakes
Here's a selection of our delicious sheet pan cakes.
Cherry Almond Cake with Cream Cheese Frosting is a lovely soft cake and great tasting. Perfect for parties too!
Deliciously refreshing lemon upside-down cake recipe, fluffy lemon sponge with a layer of sharp lemon curd to give a great combination. A great family-sized cake recipe, perfect for afternoon tea or a party.
Strawberry Shortcake Cake, a wonderful refreshing classic sponge cake packed with fresh strawberries and a whipped cream frosting.
Strawberry and Coconut Poke Cake with Fresh Whipped Cream. Easy made from scratch recipe. Yummy!
Pineapple and Coconut Poke Cake.
A delicious pineapple combined with creamy coconut cake recipe, topped with fresh whipped cream and more coconut, making a soft and fluffy great tasting tropical cake
A quick & easy made from scratch recipe with a delicious streusel crumble topping. Great tasting simple cake recipe. Perfect for dessert or tea time
Easy Homemade Pineapple Cake.
Soft and fluffy cake loaded with juicy sweet pineapple gives a flavourful dessert. Easy simple recipe for a delicious homemade pineapple cake, made from scratch.
Lazy Daisy Rhubarb Oatmeal Cake.
Just like grandma used to make, old-fashioned Lazy Daisy Oatmeal Cake with rhubarb, delicious served warm, this gooey gooey cake is a great dessert!
Easy Homemade Rhubarb Cake. Quick & easy made from scratch recipe with a delicious cinnamon streusel crumble topping. Great tasting sweet & tangy cake. Great for dessert or tea time
Pineapple Zucchini Cake, a lovely soft cake with shredded zucchini, pineapple, nuts, raisins and spices. Smells fabulous when it's baking! Easy recipe. Instructions for baking in a loaf pan or sheet pan
Easy Pineapple Upside Down Cake. This is a very easy, made from scratch recipe. The cake is so soft and moist, bursting with pineapple flavor. Delicious served simply on it's own or with some ice cream or whipped cream. Easy, fuss free recipe using regular ingredients and so good!
Easy Red Velvet Party Cake recipe with a lovely cream cheese frosting. Soft, fluffy and so delicious! Make as a sheet or round cake, you decide!
Gold Miner's Almond Joy Cake. A super moist, delicious and rich cake loved by all! Loaded with chocolate, marshmallows, coconut, almonds... this is a pretty amazing cake and perfect for parties too!
Old fashioned Oatmeal Cake with Caramel Icing. A wonderful moist, fluffy, soft sheet cake, using oats and apple sauce. Tastes like carrot cake! Easy homemade recipe and a family favorite.
Honey Bun Cake! This is a delicious, moist cinnamon and brown sugar cake, and always popular with the family!
Easy Strawberry Upside-down Cake is REALLY EASY! Uses simple ingredients and the cake turns out soft and fantastic tasting.
Pineapple and Walnut Cake is a lovely sheet style cake with crushed pineapple and nuts. There's also a really easy cream cheese frosting for the top of the cake
Coffee Cream Cheese Frosting.
A quick and easy recipe for a buttery coffee cream cheese frosting, perfect for cakes, cookies and other desserts.