1Preheat oven to 375 degrees F (190 degrees C). Grease 12 muffins cups or line with paper liners.
2Whisk oil, milk, and eggs together in a bowl. Combine flour, sugar, baking powder, and salt together in a separate bowl; fold in strawberries, blueberries, and jam. Stir milk mixture into flour mixture until just combined. Fill muffin cups with batter.
3Bake in the preheated oven until a toothpick inserted in the center of a muffin comes out clean, about 25 minutes. Cool in the muffin tin for 10 minutes before removing to cool completely on a wire rack.