Mix broth and rice together in a pot and bring to a boil. Reduce heat to low and simmer, covered, until broth is absorbed, about 20 minutes. Remove from heat.
Heat olive oil in a skillet over medium heat; add onion and garlic. Cook until nearly soft, about 3 minutes. Add mushrooms. Cook until they reach your desired texture, 5 to 7 minutes. Remove from heat and season with salt and pepper, reserving excess liquid.
Transfer the mushroom mixture to the pot with the rice. Add cream of mushroom soup and stir together evenly.