Preheat the oven to 375ºF and line a baking sheet with parchment. In a medium bowl, stir together the cream cheese, Monterey jack, sour cream, scallions, garlic, cilantro, chili powder, and salt.
Carefully slice each jalapeño down the center, lengthwise. Use a spoon to scrape out the ribs and seeds. Dip your fingers in the cooking oil and spread the oil over the outer surface of the peppers.
Spoon about 1 Tbsp of the filling into each hallowed jalapeño half. Arrange the peppers on the prepared baking sheet in a single layer (use two baking sheets if necessary).
Bake the peppers in the preheated oven for 18-22 minutes, or until the peppers have softened and the cheese on top is slightly browned. Serve hot.
Because pepper sizes vary, the cheesy filling may not be exact for 24 pepper pieces. The pepper size will also affect the cooking time, so watch the peppers closely.