In a mixing bowl, combine flour, salt, sugar, and yeast. Add warm water and olive oil, mix until a dough forms.

Knead the dough on a floured surface for about 5 minutes until smooth, then let it rise for 30 minutes.

In a skillet, cook the ground beef until browned. Add pizza sauce, Italian seasoning, bell peppers, and onions. Stir to combine and heat through.

Preheat the oven to 375°F (190°C). Roll out the dough into circles.

Place a portion of the filling on one half of the dough circle, fold over, and seal the edges.

Place calzones on a baking sheet and bake for 20-25 minutes until golden brown.